I have a ContentControl where I want to load the page myPage2. My XAML Codefrom this page looks like this:
There is no reason to use a Page within a ContentControl. A Page is a subclass of the UserControl class that adds support for being used within a Frame control to support navigation, back stack/history, etc. You should probably replace Page with UserControl in XAML and code behind, so you would end up with something like this:
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You can put the UserControl itself in a DataTemplate if you want to use it as a DataTemplate in a ContentControl: